Tuning the Conductivity Type in Monolayer WS2 and MoS2 by Sulfur Vacancies

While n‐type behavior appears to be more common in as‐prepared two‐dimensional (2D) transition metal dichalcogenides (TMDCs), substitutional doping with electron accepting atoms is typically required to tune the conductivity to p‐type in order to facilitate their potential application in different devices. Herein, a systematic study is reported on the equivalent electrical “doping” effect of single sulfur vacancies (V1S) in monolayer WS2 and MoS2 by studying the interface interaction of WS2–Au and MoS2–Au contacts. Based on the first principles calculations, it is found that the V1S can significantly alter the semiconductor behavior of both monolayer WS2 and MoS2 so that they can exhibit the character of electron acceptor (p‐type) as well as electron donor (n‐type) when they are contacted with gold. For relatively low V1S densities (approximately <7% for MoS2 and <3% for WS2), the monolayer TMDC serves as electron acceptor. As the V1S density increases beyond the threshold densities, the MoS2 and WS2 play the role of electron donor. The significant impact V1S can have on monolayer WS2 and MoS2 may be useful for engineering its electrical behavior and offers an alternative way to tune the semiconductor TMDCs to exhibit either n‐type or p‐type behavior.